Thermionic tube



May 2, 1933. c s. FRANKLIN THERMI ON I C TUBE Filed July 29, 1930 ,/r////////V// /E///////r INVENTOR CHARLES s. FRANKLIN BY %g 7 M'u- VL- ATTORN EY l atented May 2, 1933 UNITED STA TES isoa ss PATE? 'FFCE' CHARLES SAMUEL FRANKLIN, OF LONDON, ENGLAND, ASSIGNOR TO` RADIO CRPORA- TION OF AMERICA, A CORPORATION OF DELAEVARE THERMIONIC 'rUBn .Application filed July 29, 1930, Serial No. 471,*153, and in Great Britain August 16, 1929.

This invention relates to thermionic tubes or valves, and more particularly to thermionic valves of large power, adapted to generate high frequency alternating current. Such valves consist generally of an oil or water cooled anode, which may form part of the outer case of the valve, a cylindrical grid, and a filament, the latter two electrodes being, in constructions at present in common use, supported by the containing glass case which thus serves the triple purpose of eXcluding air and supporting and insulatng the grid and filament.

Large valves constructed in this manner, however, are not as rigid as is desirable, and, due to mechanical weakness an unequal eX- pansion of the glass and metal parts under the influence of heat, the grid, filament, and anode are liable to move relatively to one another, thus altering the electric constants of the valve and rendering its performance Unstable.

The principal object of the present invention is to provide a valve in which this and similar de'ects are avoided.

The invention is illustrated in the figure of the accompanying drawing, which shows in schematic section one form of construction in accordance with the said invention. In the figure, A represents the anode, G the grid, F the filament, B the band supporting the grid, and C the glass work at the base of the valve. According to the invention, the band B does not form the whole support for the grid system, the said grid system being provided with additional support at the end remote from the glass work. This additional support is provided by means of an insulator M which carries a cap K serving both to act as a corona shield for the insulator and also to hold the grid system G centrally with respect of the anode,

the end of the said grid system being attached as shown to the cap K. The top part of the said cap K is formed with ring or annular corrugations after the manner of the operative member of an aneroid barometer, the arrangement being such that while the said grid system is held centrally with respect to the anode, it is free to a limited degree to move axially, and deformation due to expansion of i heating is prevented. 'It

will be seen that with the Construction shown there will be little if any liability for the relative positions of the electrodes to change, and in consequence the electricalcharacteristics of a valve made'as shown in accordance with the invention will remain constant after a long period of life.

A further advantage of the arrangement Although not limited to its 'application thereto, the invention is particularly advan- V tageous in connection with valves intended to be employed 'or accurately constant high frequ-ency generation.

Having described the nature of my said invention, what I claim is 1. A thermionic tube having grid and anode electrodes, a press for supporting the grid, additional supporting means for said grid comprising a metal cap formed on one side with corrugations and located centrally within the anode by an insulator carried in the end thereof, the arrangement being such that the cap prevents transverse movement of the grid with respect to the anode while permtting limited longitudinal movement. a

2. In an electron discharge device, having an evacuated envelope, an electrode mounted therein, and supports for said electrode at each end of the envelope, one of said supports including a yieldable connection comprsing a a corrugated member.

3. In an electron discharge -device, h-aving an evacuated envelope, an electrode mounted therein, and supports for said electrode at each end of the envelope, one of said supports including a yieldable connection comprising a transverse member having corrugations.

4. In an electron discharge -device, having an evacuated envelope, an electrode mounted of the grd electrode.`

theren, `and supports for said electrode at each end of the envelope, one of said supports including a yeldable connection comprising a transverse member having corrugations and nsulated from the electrode.

5. In an electron discharge tube having grid and plate electrodes, means for maintaining a fixed spacial relation between said electrodes in a lateral direction While permitting limited longitudinal,movement, comprising an nsulating member supported by the plate electrode adjacent to one end of the grid electrode, and a second member carried by said insulating member having a corrugated surface for engagng With the said end 6. In an electron discharge tube, anode and grid electrodes, and means for preventing lateral movement of the grd With respect to the anode While permtting limited longitudinal movement comprsing an nsulated transverse member interposed between &djacent ends of said electrodes having annular corrugations engaging with and yield ably supporting said grd electrode.

7. In an electron discharge tube Wheren the anode is closed at one end and comprises a part of the exhausted envelope, a grd electrode within the ano de, and means for yieldably supporting one end of the grd electrode from the closed end of the anode, comprisng an insulating member fiXedly attached to the closed end of the :mode and a yieldabl-e mem-` ber carried by said insulating member abutting the &dj-&Cent end of the grd electrode.

CHARLES SAMUEL FRANKLIN. 

